A key witness against two men charged in a "blatant execution-style" murder says he won't testify at their trial unless federal immigration authorities drop their effort to deport him.

"They either let two murderers go free, or they don't deport me," Vimal Singh said in an interview at Sacramento's downtown jail, where he is being detained as a material witness.

Deputy District Attorney Michael Kane declined to comment on the importance of Singh's testimony. Michael Wise, the lawyer who is representing Singh in his capacity as a material witness, said he's been told "secondhand" that his client's observations are "pretty critical."

According to court papers filed in the case, Singh saw two burly masked men – one of them armed with a rifle – walk into an electronics warehouse in the middle of the night. He heard gunfire and saw the men come out. Then they shot at him, and Singh sped off in his car without getting hit.

Police identified the men as Wayne Albert Caskey, 46, and Bennett Louis Kovac, 45. Jury selection in their murder trial got under way earlier this week in Sacramento Superior Court.

Caskey and Kovac are accused in the 3:30 a.m. shooting death of Gary R. Brooks, 45, on June 11, 2006, inside his father's electronics business. Prosecutors say they don't know the motive for the killing, which Kane described as "a blatant execution-style murder."

Preliminary hearing testimony and court papers filed by the prosecution showed that Singh had been smoking methamphetamine with Brooks around 2 a.m. the morning of the murder, left the warehouse at 3:10 a.m. and then came back around 3:25 a.m. to do some more drugs when he saw the masked men.

Singh, 36, is a resident legal immigrant who moved to the United States from his native Fiji in 1979. He has been imprisoned twice, for car theft and second-degree burglary, in a criminal record that dates to 1990.

He says his bad past resulted mostly from a drug problem he's wrestled with since elementary school days. He said he's been clean and sober for more than two years.

Immigration and Customs Enforcement spokeswoman Virginia Kice said her agency has classified Singh as an "aggravated felon," based on his criminal record.

An immigration judge ordered Singh deported in February, but the case has been forestalled on appeal. Kice said if the 9th U.S. Circuit Court of Appeals upholds the judge's order, "ICE will move forward with his deportation."

Kice said immigration authorities conferred with Sacramento prosecutors to "defer his removal" to Fiji.

"If and when he finishes with local authorities, he'll come back to ICE custody and we'll have to await a decision by the 9th Circuit," Kice said.

Married and with four children, Singh, who drives a tow truck, says whatever arrangement ICE made with the local DA doesn't work for him and that he won't take the stand against Caskey and Kovac.

"I won't do it," he said. "Look what INS (the old immigration agency) is trying to do to me. I'm losing my family."

McGeorge School of Law professor John Myers said Singh has a legal obligation to testify and can be held in contempt of court if he refuses. But that doesn't mean he has to say anything once he's on the stand.

"It sounds to me like he's trying to get a deal for himself, and more power to him if he can," Myers said. "You can't force him to testify. He could have some leverage."

Singh is not the only witness in the case. Another witness, according to prosecutors, said both Caskey and Kovac individually told him about their meeting with Brooks and how Caskey ultimately shot and killed the man.

Others said they saw Brooks engaged in "an argument or at least a serious conversation with a person named Wayne" the night before the killing, according to prosecutors' court papers.

Caskey is charged with firing the .223-caliber rifle that prosecutors say is the murder weapon. Kovac is accused of having been armed with the gun.

State corrections records show that Caskey has been to prison five times since 1983 on drug, weapons and other charges. Kovac had a pending methamphetamine possession for sales case at the time of the shooting and has one other drug conviction, but he has never been to prison, according to corrections records.

After their preliminary hearing, Deputy DA Kane said in court that the motive for killing Brooks was "unclear" and that "whatever it was would have to be considered a trivial motive."

In arguing against bail for the two, Kane said they "executed a man for what appears to be no reason or very little reason at best and ambushed him in the middle of the night with masks on," according to the hearing's transcript.